Question: Solve for $r$ : $r - 17 = 18$
Answer: Add $17$ to both sides: $ \begin{eqnarray} \\ r - 17 &=& 18 \\ \\ {+17} && {+17} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{-17 + r} &\hphantom{=}& \hphantom{18} \\ r &=& 18 {+ 17} \\ \end{eqnarray} $ Simplify. $ r = 35$